The human heart is divided into four chambers. They are the right atrium, the right ventricle, the left atrium, and the left ventricle. The right atrium and right ventricle are divided from the left atrium and left ventricle by a wall called the septum. The atrial septum separates the atria, and the ventricular septum separates the ventricles.
Typically, blood flow through the chambers of the heart is directed through the cardiac valves. There exists a cardiac condition, however, in which blood can shunt from one chamber to another through the septum. This is generally referred to as a septal defect.
In the atrial, these septal defects are referred to as atrial septal defects (ASDs). One type of ASD is a patent foramen ovale (PFO). A PFO results when tissues that were used during fetal development to provide a passage (the “foramen ovale”) to shut blood from the right atria to the left atria, thereby bypassing the fetal lungs, fail to fuse shortly after birth. As a result, the foramen ovale remains potentially viable, or “patent.”
Given the right circumstances, the pressure in the right atrium can exceed that in the left atrium, allowing blood to shunt from the right to the left atrium through the PFO. This would typically be inconsequential, except when the venous blood from the right atrium contains thrombotic debris that would normally travel to the lung to be eliminated by thrombolytic mechanisms. In this case, the thrombotic debris (e.g., a blood clot) can travel to the left atrium where it can potentially cause a myocardial infarction or a stroke.
To close such defects, open surgery may be performed to ligate and close the defect. Such procedures are highly invasive and pose substantial morbidity and mortality risks. Alternatively, catheter based procedures have been developed involving introducing umbrella-like structures into the heart that include opposing expandable structures connected by a hub. One of the expandable structures is inserted through the defect, and both are expanded to secure the tissue surrounding the defect between the structures in an attempt to seal and close the defect. Such structures, however, involve frame structures that support tissues, both of which may fail during the life of the patient being treated, opening the defect, and/or releasing segments of the structure within the patient's heart.
Accordingly, apparatus and methods for closing patent foramen ovale, or other septal defects would be considered useful.